Three weeks was supposed to be the big milestone in starting to determine the success of the rest/rehab/PRP injection treatment plan for Masahiro Tanaka's partially torn right UCL. That milestone was reached last week and all indications are that the treatment has worked so far. Tanaka was examined by the Yankees' team doctor on Friday and cleared to start throwing again. Had he not been cleared, the plan probably would have been scrapped and TJS would have been scheduled.
Now that's still a possibility, as there's no way of knowing how healed Tanaka's UCL is and how long it will be able to hold up to the rigors of throwing and pitching again. But the plan was for him to throw today if he was cleared and, via Wally Matthews, that's exactly what he's going to do:

That source was not Brian Cashman or Joe Girardi, so take the quote however you want. Joe wouldn't comment one way or another, but honestly, if Tanaka wasn't going to throw today the team would just come out and say it. There's nothing to be gained by being cryptic about something that's not going to happen, so I'm going to take Wally's source's word and chalk it up as a positive. Today's throwing session won't be anything more than playing catch. Tanaka is probably at least a month away from returning to game action. But this next step is a much better one than the other potential next step. Right?